Hitherto, a square battery is known as a battery in which a higher volume density is obtained as compared with a cylindrical battery. In the square battery, a wound body formed by laminating and winding a band-like positive electrode and a band-like negative electrode together with a separator therebetween is contained in a square battery case, and an electrolyte is injected in the battery case.
In the square battery, non-coating parts of the positive electrode and the negative electrode are respectively protruded at both ends of the wound body in a winding axis direction, and electrode terminals or current collectors are connected to the non-coating parts, so that connection resistance is reduced by minimization of an energizing path, and the output is raised. Besides, this structure is effective also in compacting.
With respect to a connection form between a wound body and a current collector, for example, an electric storage device of patent document 1 is proposed.
In the electric storage device disclosed in patent document 1, a plate-like sheet connection part is inserted inside from an end surface of a non-coating part protruding from the wound body and both are connected.